Cell growth necessitates precise timing of a number of cell events such as DNA replication, chromatin formation, and chromosome alignment. A number of checkpoints in this process acts to insure that events leading to cell division occur in the proper sequence (i.e., cell division doesn't occur before chromosome segregation). Oxygen radicals may play a role in this synchrony, perhaps as signaling molecules. Nitroxides are well-known superoxide dismutase mimetics and, in presence of some transition metals, catalase mimetics. Therefore, they may interfere with the synchrony of cell division. We show that growth of BHK (baby hamster kidney) cells is accelerated by 0.1 to 0.2 mM and inhibited by 0.4 to 1.0 mM Tempol (2,2,6,6-tetramethyl piperidine-N-oxyl-4-ol) in the growth media. Tempol in the range of 0.4 to 1.0 mM does not kill the cells. This suggests that growth of BHK cells may be mediated by oxygen radicals. This work relies on a software package developed in a close collaboration with the IERC; the software is constantly updated to accommodate the needs of this project.